Cutter



Q. E. STAPLES Nov. 21, 1950 CUTTER 4 Sheets-Sheet 1 Original Filed Sept. 22. 1943 BY 77m 8 firroe/vifrs Nov. 21, 1950 o. E. STAPLES 2,530,550

' CUTTER V Original Filed Sept. 22, 1943 4 sheets-Sheena uvmvzm FIG. 4 0775 5. 5774/5255 8? W 3% WW I M 27 Hi TZ/vEYa 0. E. STAPLES Nov; 21, 1950 CUTTER 4 Sheets-Sheet 3 Original Filed Sept. 22, 1943 w W 5 E m,

flrroe/wsi's I BY .7 7 I Nov. 21, 1950 o. E. STAPLES 2,530,550

CUTTER Original Filed Sept. 22, 1943 4 Sheets-Sheet 4 INVENTOR. 0775 if STAPLES a BYWIB,;%I

/A 'WQMZ Patented Nov. 21, 1950 UNITED STATES PATENT OFFICE CUTTER.

Qtis E. Staples, Euclid, Ohio, assignor to. The Cleveland Hobbing Machine Company, Euclid, Ohio, a corporation of Ohio '5 Claims.

The present invention relates to tools or cutters of the type employed in machines of the character disclosed in Theodore F. Carlin U. S. Patent No. 2,233,399 and the present application is a division of my copending application Serial No. 743,655 filed April 22, 1947, which application is, in turn, a continuation of my application Se,- rial No. 503,373, filed September 22, 1943, and now abandoned.

The principal object of the present invention is the provision of a novel and improved turning cutter adapted to be rotated about an axis angularly disposed and ofiset with respect to the axis of rotation of the work and capable of forming articles having cylindrical or tapered portions connected by shoulders and which cutter comprises cylindrical sectors radially ofiset with respect to each other and having arcuately-shaped cutting edges at their upper ends and a top rake angle, which cutting edges are connected by shoulder cutting edgesinclined to the axis of rotation of the tool at the top of an inclined, generally radial surface toprovide a clearance angle.

Further objects and advantages of the invention will be apparent'to those skilled in the art to which it relates, from the following description or explanation and the accompanying drawings form a part of this specification, in which Fig. 1 is a diagrammatic view illustrating that part of the method of the invention wherein the cutter is calculated and/or laid out, disregarding the top rake and clearance angles;

Figs. 2 and 3 are diagrammatic views illustrating the method of determining the corrections to the radii of the arcuate cutting edges shown in Fig. 1 incident to top rake and clearance angles;

Fig. 4 is an enlarged view of a portion of Fig. 3;

Fig. 5 is a diagrammatic View illustrating that part of the method wherein the side clearance angle for the cutting edges which form the shoulders is determined;

Figs. .6 and '7 are diagrammatic views illustrating the method of determining the correction. .for the-shoulder forming edges incident to the top rake angle; and

Figs. 8', 9. and 10 illustrate a method of grinding the shoulder forming edges.

As previouslystated, the present invention. relates to cutters :and cams of the character em.- ployed on machines. of the type disclosed in U. S. Patent No. 2,233,399. Reference to said patent will show that the machinedisclosed therein resembles a more or less conventional lathe, the details of which are not reproduced here. It is sufii'cient tonote that, as diagrammatically repby side cutting edges :onthe tool or cutter.

2 resented in: Fig. 1 of thedrawings-of this application, the work blank [5 is supported between a chuck (not shown) and a tail center 23 of the machine. The workblank' I5 is turned to the desired form by a disk orsegment-shaped tool or cutter T-rotatably supported on the tool slide of the machine for rotation about an axis offset from and angular-1y disposed to the axis of rotation of the work. In operation, the tool or cutter is fed longitudinally of the axis of rotation of the work blank'andsimultaneously rotated in a predetermined manner at variable speeds by a cam C andcam follower 32-operatively connected thereto bymechanism comprising a rack 29 and pinion 28. Alternatively, the work blank may be moved relative to the tool or cutter and cam, etc., see Theodore F. Carlin U. S. Patent No. 2,233,398. If-desired, the tool T may berotated at a uniform rate-of speed and the relative movement therebetween and the work longitudinally of the latter effected-at -a variable rate of speed, or both of'said movements may lee-effected at variable rates of speed, so long as the relative angular rotation of the tool T per unit of linear feed is varied from time to time in a predetermined manner.

In operation, the relative feed movements between :the tooland work blank, that is the relative movements therebetween except therotation of the work blank, generally speaking, are as though the cutter or tool were rolled. along the work, with the result that-the respective surfaces of the work may besaid to be generated by the tool. When therelative feed movements are such that the effect .is .atrue rolling motion between the .arcuately-shaped cutting edge of the tool or cutter and the section of :the finished work formed thereby, the cutter is herein said tube rolledaor rolling alongxthevwork without slip. If the relative feed: movements. are such thatpin efiectrthe cutter :does not'travel lengthwise of :the workas fast. as itwould: if roiled or rolling. along the work without: slip, the-cutter is said to be rolled or rolling along thework with underslip. The .reverse'condition is; referred toas. overslipi.

The present invention relates primarily to cutters as articles ofmanniacture for producing articles, having portions. of difierent diameters connected .by shoulders, which shoulders are :formed In producing work or this :nature, the relative feed movements betweenthe tool or cutter and work are preferably accomplished .by rotating the tool or cutter at variable. rates ofspeed and moving the work blank lengthwise at a uniform. rate of speed; however, it is to be understood that the tool or cutter may be rotated at a uniform rate of speed and the relative movement between the same and the work blank longitudinally or lengthwise of the axis of rotation Of the work blank effected at a non-uniform rate of speed, etc. The cutter and cam combinations must be specifically designed for each differently shaped article to be produced since the relative angular rotation of the cutter per unit of relative longitudinal movement must be varied in a definite relationship. In other words, each cutter or tool and cam combination is designed for use in connection with a particular machine and the production of a particular article.

The cutter of the present invention will be described or explained with reference to the design and layout of a cutter and cam for producing an article having a shape which is fairly characteristic of the articles which the machines of the aforesaid Carlin patents are particularly adapted to turn or produce. With the foregoing in mind, it is assumed that it is desired to make a cutter or tool and cam combination for the machine shown in the drawings of Carlin Patent No. 2,233,399 to produce an article 9 having three cylindrical portions or sections I0, II and I2, the diameters A, B and D of which are 1.000, 1.375 and 1.625 inches, respectively, connected by radial shoulders I3 and I4, from a cylindrical work blank I5 shown in dot-dash lines in Fig. 1, the outside diameter of which blank is the same as the diameter of section I2.

The first step is to empirically determine one of the following: (1) the offset E, that is, the distance between the axis of rotation I5 of the tool Or cutter and the axis of rotation I? of the work blank measured in the plane of the axis of rotation of the work blank normal to the axis of rotation of the tool or cutter; (2) the radius F of the arcuately-shaped cutting edge i8 of the tool furthest from the axis of rotation I6 of the tool T; or, (3) the radius G of the arouately-shaped cutting edge I9 nearest the axis of rotation It of the tool. These dimensions or distances are optional but when any one is once selected or determined, substantially all the other dimensions of the tool and cam are determined or fixed, and the cutter must be operated at all times in the position determined thereby.

In determining one of the three dimensions referred to above, it must be kept in mind that the radius G of the arcuately-shaped cutting edge I9 nearest the axis of rotation I6 of the tool cannot be less than the radius of the hub or like part of the tool, plus any required or desired clearance, and that the radius F of the cutting edge I8 must equal G plu one-half the difierence between the diameters of the largest and smallest sections of the article to be produced. The amount of clearance provided is largely optional but some clearance must be provided to allow for a top rake angle. Other factors that must be considered in determining or selecting the clearance are the characteristics of the machine, cutter sizes which are practical, and practical limitations of offset E. The maximum distance that the arcuately-shaped cutting edge I8 of greatest radius can be away from the axis of rotation I5 of the tool is determined by practical limits of so-called overhang consistent with other requirements, such as rigidity, minimization of chatter, etc. The offset E equals the radius of any arcuately-shaped cutting edge, plus the radius of the section of work turned thereby.

=2.000 inches B-A T =1.8125 inches The cutter or tool may, if desired, be fed into depth either lengthwise or transversely of the work, but preferably it is "rolled into depth. In either event the cutter must clear the blank at the beginning of the operation so that the blank can be readily positioned in the machine. Assuming that the cutter is to be rolled into depth by movements substantially the same as those employed to turn the initial section I0 of the article to be formed, the axis of the cutter must be located beyond the end of the work blank a distance H equal to the base of a right angle, the other sides of which are F and the distance between the axis of the cutter and the outside of the work blank plus some suitable clearance, such as, 10% of the actual amount required. Having in mind the dimensions given above, it follows that 2 =1.10,/whoop-(2.50%?) =1.180817 inches Cos I: F

angle I=32 27! 34 For convenience, this angle is corrected to the nearest degree and hence an angle of 32 is used. The mechanism for connecting the cam roller and the tool or cutter spindle, of necessity, is

such that a certain cam rise is necessary to produce a unit of rotation of the tool or cutter or vice versa. This factor of the machine is herein designated J, and assuming that in the instant machine this mechanism is such that a rotation of 1 of the tool or cutter is produced by .03 inch of cam rise, the factor J equals .03. The cam rise K required during the approach portion of the cycle of operations, that is, to rotate the cutter 32, is determined by multiplying 32 by the hitiaifito For convenience, 35, the nearest higher even angle, is used.

The cam rise N required to produce this rotation of the tool is 35 times .030 inch or 1,05 inches.

The relative movements between thecutter and work occurring while the section I is being formed, :cannot be continued after the shoulder 13 "is formed by the cutting edge 2'! connecting the cutting edges or arcs -l8 and 19 without 'destroying the left-hand corner of section II of the work. In order to prevent destruction of this corner, the speed of rotation of the cutter is accelerated temporarily sufficiently to allow the shoulder forming edge 21 to clear the shoulder I3, and thereafter continued at a reduced speed but at a speed higher than that at which it was operating during formation of the section 10. The higher speed of rotationof the cutter, during which period overslip is occurring, preferably continues until the axis of the cutter reaches a point 24, a distance P from the point 26. While the amount of overslip eifec'ted and the distance through which it continues depend upon the angle of the shoulder,etc., the amount of overslip effected is preferably about30% and the distance P through which 'it is continued is preferably equal to the length of the shoulder [3, that is, one-half the difference between the diameters of the adjacent portions i0 and il, which is {1875 inch.

From the foregoing, the preferred angle Q through which the cutter is rotated while it is traveling from the point 26 to the point 24 is calculated as follows:

For convenience, an angleof 8 is used.

The cam rise R required to produce this rotation of the tool when calculated as indicated above is .24 inch.

While the axis of the tool is traveling from the point 24 to the point 30, in line with the shoulder M, a distance S equal to the length of the portion ll minus P, the cutter 'is preferably rotated through an angle U. Assuming that the length of the shoulder I I is 1.250 inches, then S is equal to 1.0625 inches.

I Theai-igle U i 'crererabiysuch-thatfrom 10% to 20% undersli-p occurs while the cutter is traveling from the point {24 to the point 30. Therefore,

. 3x36 2 G -3. l4l-6" 40% For convenience, an'angle of 30 is employed which will produce an underslip slightly in excess of 10%. The cam rise V required to produce this angular rotation of the tool is .9 inch determined as indicated above.

In order to prevent destruction of the outer corner of the shoulder I4 by the shoulder forming edge 3| of the cutter, the rotation of the cutter is again accelerated in the same manner as previously referred to with respect to the shoulder i3. The acceleration 'isprefer'ably such that approximately 30% overslip occurs and is continued to a point 33, a distance W equal to the height of the shoulder I4, which is .125 inch. The desired angular rotation X to be --imparted to the tool during this movement is calculated as follows:

For convenience, 6 isused. The cam rise Y required to produce this rotation is .18 inch calculated as indicated above.

It will be seen, therefore, that each arcuatelyshaped cutting edge preferably has a length which is equal to %-90% of the length of the portion of the work to be turned thereby plus approximately 1 30% of the difierence between the radius of that arcuately-shaped cutting edge and the radius of the next preceding arcuatelyshaped cutting edge.

After the cutting operation has been completed, the work blank has to be removed. When possible, the cutter is preferably made segment-like in shape so that the cutter can, in eifect, be withdrawn from the work by continuing its rotation for a short period. This is accomplished by continuing the feed movement and extending the cam slightly. Any suitable cam rise can be employed depending upon the speed with which it is desired to have the tool move clear of the work.

Two of the numerous positions assumed by the cutter or tool as ittravels lengthwise of the work blank are indicated by dot-dash lines in Fig. 1. The reference character 32 designates the cam roller which cooperates with the cam C to effect the rotation of the cutter, and a number-of the ment provides the necessary clearance angle even though the periphery of the cutter is cylindrical. The cutting edge of greatest radius is preferably operated slightly below center and the distance that the other edges are below center will depend upon the amount that they are set back with re spect to the cutting edge of greatest radius and upon the value of the angle of top rake.

Because the cutter under consideration is to be operated in such a position that the arcuatelyshaped cutting edges i8, etc., out below the center plane of the work blank, the radii of the cutter previously determined must be increased incident to the curvature of the blank. Preferably the corrected diameters of the arcuately-shaped cutting edges are determined in the following manner. An arbitrary radius a not less than F, plus .030 to .050 inch, is assumed as the intersection b of the surface 38, produced by the top rake angle extended, with the plane 35 of the axis of rotation of the work perpendicular to the axis of rotation of the tool. It has been found that with a normal top rake angle of about 25 this gives about the minimum clearance angle at which the cutting edge of greatest radius can be efficiently operated.

Referring to Figs. 2, 3 and 4, d and e are the corrected radii of the arcuately-shaped cutting edges I8 and 19, respectively, for producing or turning the sections 10 and H of the work. Assuming that the top rake angle 0 is and that a equals F+.050 inch, that f is the intersection of the surface, 36 of the tool with the cutting edge 48 thereof, that g is the intersection of the plane 35 with the axis of rotation H of the work, and that h, i, and 1' are the sides of the triangle b, j, and g opposite the angles 1), f, and g, respectively, then =.500 inch i=E -a =Ai50 inch sin b h 'The amount 0 to be added to F as the correc tion incident to the location of the cutting edge l8 below the plane 35 is calculated as follows:

= .0005 inch The clearance angle m is the same as the angle g or 2 38' 40". As shown in Fig. 4, the angles 9, etc., are exaggerated for clearness.

The correction o for radius G is figured in a similar manner and in the example given is .00836 inch. The clearance angle in the case of the cutting edge I9 is then 8 56 30".

The minimum side clearance angle n on the shoulder forming cutting edge 21 is determined by the angle at the point of maximum undercut, that is, the angle at the point where the radially outer end of the shoulder forming cutting edge 2? undercuts the blank l5 to the greatest extent, see Fig. 5.

The cosine of the angle p at which maximum undercut occurs is equal to Z, that is, the distance from the center I 6 of the cutter to the outside diameter of the work blank, divided by G, the radius of the arcuate cutting edge IQ of lesser radius; in other words,

Cos 1 3 therefore,

L p=2l24'12 For convenience, 22 will be employed.

lc=h cos g =.500 .9989333 -=.49946 inch d=E-k:

-=2.500-.4995 =2.0005 inches Then the tangent of n, the minimum side clearance angle, is equal to q, the depth of undercut, divided by r, one-half the chord of the circle of outside diameter of the blank at the 1 height of undercut s, or the square root of 1% times 3 where t is equal to the diameter D of the work blank l5 minus s. The depth of undercut q is equal to the tangent of the angle of maximum undercut multiplied by the length of undercut u, that is, the length of the shoulder forming edge 21.

Expressed mathematically,

q =tan pXu =tan 22(FG) =.40403(2.0001.8125) .07575 inch 8 =W=J F G +F s =0.202 inch t D-s 1.423 inch Therefore, the minimum clearance angle np=8 2" 4".

For convenience, this angle is increased to an even angle. In practice it has been found that a side clearance angle of 10 works satisffactorily in most instances and is usually employed.

In laying the tool out in a plane normal to the axis of rotation thereof and including the axis of rotation of the work; blank, the radial angle of the cutting edge or edges forming the shoulders must be corrected by an amount equal to 12, see Fig. 6, to compensate for the effect of top rake and side clearance if the shoulder being formed is to be held to a desired predetermined angle.

Assuming that the top rake angle is 25 and that the side clearance angle 11 is 10, then the tangent of the correction angle 1; fora square shoulder is equal to the tangent of c multiplied by the tangent of n or Tan 11 tan 0 x tan n Therefore,

greater radius with the shoulder cutting edge.

The relative positions of the cutter and grinding Wheel are shown in Figs. 8, 9, and 10; wherein the reference characters as and M designate, respectively, a grinding wheel and its axis of rotation.

In the event that the adjacent. cylindrical sec tions of the blank are to be connected by a chamfer or bevel instead of by a right-angular shoulder, the correction angle for the cutter shoulder forming edge, corresponding with angle '0 above, is figured in the following manner. Referring to Fig. 7 wherein theparts corresponding with parts previouslyreferred to-aredesignated by the Same reference characters with a prime mark affixed thereto, the cylindrical portions l9 and II of the work are connected by a shoulder or bevel [3, making an The angle 0 subtended by the chamfered or beveled surface 27' of the cutter is as follows:

0=l80(y+:v)

)\=sin 0 F' =.17952 inch e=(F cos 0) -G 794 inch u=FG =.1875 inch =tan cXu =tan 25 .1875

=.0875 inch 5=tan nXyb =tan 10 0875 =.Ol543 inch Cotan z= i In the foregoing illustration the uncorrected radii F and G were used. Theoretically, the corrected radii would. produce more accurate results; however, from a practical point of View the uncorrected radii are satisfactory since the error resulting from the use thereof less than present manufacturing tolerances.

The equations just derived with respect to Fig. 7 are general and may be used to determine the correction angle 1; for the cutting edge of a tool adapted to farm a shoulder of any predetermined angle 10 on the work. To facilitate the determination of the angle 1) it is desirable to express the equation:

in difierent form. Remembering that:

e=(F' COS t9)G' A=F" sin 0 6: 0 tan n =u' tan 0 then (F cos'0) G cot z= tan z=tan tan n Moreover, since and tan v'=tan 0 tan 11' Hence, the general equation reduces to the simple form previously given when a square shoulder is to be formed on the work.

When it is desired to form a shoulder on the work having any predetermined angle w, the setting of the grinding wheel 4|] to form the shoulder cutting edge 2'! on the tool must be such that the working face of the wheel is inclined to make an angle a=Lw-LD' with a plane extending from the outer edge of the arcuately-shaped cutting surface of greater radius perpendicular to a radial line, extending from the axis of the tool through the intersection of the arcuately-shaped cutting surface of lesser radius with the shoulder cutting surface. When the shoulder to be formed on the work is square, this inclination of the grinding wheel is simply expressed as being equal to the correction angle measured from the radial line through the intersection of the outer edge of the arcuatelyshaped cutting surface of greater radius with the shoulder cutting edge, the inclination being in the direction which increases the angle that the shoulder cutting surface makes with the arouate cutting surface of greater radius.

After the cutters have been calculated and/0r laid out in the manner described, they may be rough formed by conventional equipment in any suitable manner, hardened, and then ground to final size and shape. The side or shoulder cutting edges can be ground by employing a conventional grinding machine having a flat faced grinding wheel, means to produce a feed between the wheel and the work, and a work support which may be adjusted to present the work to the face of the grinding wheel at the angles determined as described above.

From the foregoing explanation it will be apparent that the objects of the invention heretoa new and improved cutter has been provided. While the invention has been described in con siderable detail, it will be apparent that certain changes may be made within the scope of the invention, and it is my intention to cover hereby fore illustrated have been accomplished and that 12 all adaptations, modifications and uses of the invention disclosed herein.

Having thus described my invention, I claim:

1. A tool or cutter adapted to be rotated about an axis for forming an article having portions of different diameters connected by shoulders, said tool comprising radially ofiset cylindrical surfaces having arcuately-shaped cutting edges at their upper ends forming a portion of the circumference of the tool, the said arcuately-shaped cutting edges each being provided with top rake of a selected angle, and a shoulder cutting edge at the upper end of a generally plane surface inclined to the axis of rotation of the tool at an angle equal to the desired clearance angle connecting adjacent arcuate cutting edges.

2. A tool or cutter adapted to be rotated about an axis for turning an article having portions of different diameters connected by shoulders, said tool comprising: radially offset cylindrical surfaces having arcuately-shaped cutting edges forming a portion of the circumference of the tool, the length of each of said arcuate cutting edges being approximately %-90% of the length of the portion of the work to be turned thereby plus approximately 130% of the difference between the radius of said arcuate cutting edge and the radius of the next preceding arcuate cutting edge; the said arcuate cutting edges each being provided with a top rake of a selected angle; and adjacent arcuate cutting surfaces being connected by a shoulder cutting edge at the upper end of a generally plane surface on said tool inclined to the axis of rotation of the tool at an angle equal to the desired clearance angle, the said shoulder cutting surface being also inclined to a plane, extending from the outer edge of the shoulder cutting surface perpendicularly to a radial line of the tool extending through the intersection of the shoulder cutting surface with the adjacent arcuately-shaped cutting surface having the lesser radius, at an angle substantially equal to 42), where cot z- G sin y F! sin :0:

c'=the top rake angle n'=the side clearance angle.

3. A tool or cutter adapted to be rotated about an axis for forming an article having portions of different diameters connected by shoulders, said tool comprising radially oifset cylindrical surfaces having arcuately-shaped cutting edges at their upper ends forming a portion of the circumference of the tool, the said arcuateiy-shaped cutting edges each being provided with top rake of a selected angle, and a shoulder cutting edge at the upper end of a generally plane surface inclined to the axis of rotation of the tool at an angle equal to the desired clearance angle connecting adjacent arcuate cutting edges, the said shoulder cutting edge being also inclined to plane which extends from the outer edge of the shoulder cutting edge perpendicularly to a radial line of the tool extending through the intersection of the shoulder cutting edge with the adjacent arcuately-shaped cutting edge having the lesser radius.

4. A tool or cutter adapted to turn an article having portions of dififerent diameters connected by shoulders, said tool comprising: radially offset cylindrical surfaces having arcuately-shaped cutting edges forming a portion of the circumference of the tool, the length of each of said arcuate cutting edges being approximately 80%- 90% of the length of the portion of the work to be turned thereby plus approximately 130% of the difierence between the radius of said arcuate cutting edge and the radius of the next preceding arcuate cutting edge; the said arcuate cutting edges each being provided with a top rake of a selected angle; and adjacent arcuate cutting surfaces being connected by a shoulder cutting edge at the upper end of a generally plane surface on said tool inclined to the axis of rotation of the tool at an angle equal to the desired clearance angle, the said shoulder cutting edge being also inclined to the plane which extends from the outer end of the shoulder cutting surface perpendicularly to a radial line of the tool extending through the intersection of the shoulder cutting edge with the adjacent arcuately-shaped cutting edge having the lesser radius.

5. A tool or cutter adapted to be rotated about an axis for forming an article having portions of different diameters connected by shoulders, said tool comprising radially offset cylindrical surfaces having arcuately-shaped cutting edges at their upper ends forming a portion of the circumference of the tool, the said arcuately-shaped cutting edges each being provided with top rake of a selected angle, and a shoulder cutting edge at the upper end of a generally plane surface inclined to the axis of rotation of the tool at an angle equal to the desired clearance angle connecting adjacent arcuate cutting edges, the said shoulder cutting edge being also inclined to a plane, extending from the outer edge of the F'=radius of the adjacent arcuate surface of greater radius,

G=radius of the adjacent arcuate surface of lesser radius,

y=the angle of the shoulder to be formed G sin y T c'=the top rake angle n=the side clearance angle.

OTIS E. STAPLES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 386,013 Howe July 10, 1888 1,632,528 Zeidler June 14, 1927 

